Driveline clutches are used to selectively rotationally couple first and second rotatable driveline components. Limited-slip driveline clutches are driveline clutches that selectively couple first and second rotatable driveline components while concurrently permitting a limited/controlled amount of relative rotation between the first and second rotatable driveline components. One application for a limited-slip driveline clutch is in a differential where the driveline clutch is used to limit the rotational slip that can occur within the differential.
A differential is a component of an axle assembly that is used to transfer torque from a drive shaft to a pair of output shafts. The driveshaft drives the differential through the use of a bevel gear that meshes with a ring gear mounted to a housing of the differential. In automotive applications, a differential allows the tires mounted at either end of the axle assembly to rotate at different speeds. This is important when the vehicle is turning because the outer tire travels over an arc of greater distance than the inner tire. Thus, the outer tire must rotate at a faster speed than the inner tire to compensate for the greater distance of travel. The differential includes a gear arrangement that allows torque to be transferred from the driveshaft to the output shafts while concurrently allowing the output shafts to rotate at different speeds as needed.
While differentials are useful in cornering, they can allow vehicles to lose traction, for example, in snow or mud or other slick mediums. If either of the drive wheels loses traction, it will spin at a high rate of speed and the other wheel may not spin at all. To overcome this situation, limited-slip differentials have been developed to shift power from the wheel that has lost traction to the wheel that is not spinning.
Limited-slip differentials have been developed that use a hydraulically actuated clutch to limit differential rotation between the output shafts of the differential. Such limited-slip differentials can include a pump in the form of a gerotor incorporated into the differential housing. Solenoid valves have been used to precisely control the actuation pressure provided to the clutch. However, to be operable, such valves require an electronic controller and valve control hardware/software. This can be expensive. In contrast, a simple orifice is a relatively inexpensive structure that has been used in combination with a hydraulic pump to generate hydraulic pressure for actuating the clutch. However, a non-compensated orifice will provide very different actuation pressures depending upon the rate of flow output from the hydraulic pump. Example limited-slip differentials are disclosed at U.S. Pat. Nos. 4,012,968; 5,310,388; 6,332,522; 6,733,411; 6,789,657; 7,361,144; 7,448,482; and 8,043,184.